Gas handler, riser assembly, and method

ABSTRACT

Method, riser assembly and gas handler for diverting gas from a riser. The riser assembly includes a riser having a first end and a second end and a conduit extending from the first end to the second end; a gas handler connected to the riser and provided between the first end and the second end, the gas handler having an external casing; plural pipes attached to an outside of the riser such that at least one pipe of the plural pipes enters through the external casing; and a gas vent pipe configured to start at the gas handler and extend towards the second end of the riser and the gas vent pipe is further configured to divert a gas from the gas handler through the outside of the riser.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to and thebenefit of, U.S. patent application Ser. No. 12/956,218, which was filedNov. 30, 2010, the full disclosure of which is hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the subject matter disclosed herein generally relate tomethods and systems and, more particularly, to mechanisms and techniquesfor subsea drilling.

2. Brief Description of Related Art

During the past years, with the increase in price of fossil fuels, theinterest in developing new production fields has dramatically increased.However, the availability of land-based production fields is limited.Thus, the industry has now extended drilling to offshore locations,which appear to hold a vast amount of fossil fuel.

However, a problem posed by the underwater exploration, and especiallydeep water exploration, is the control of gas in the marine riser. Themarine riser (or a lower marine riser package) is essentially a pipemade of many components that connects a rig or vessel that floats at thesurface of the water to a blowout preventer provided undersea at a wellhead. These elements are shown in FIG. 1. More specifically, an oil andgas exploration system 10 includes a vessel (or rig) 12 having a reel 14that supplies power/communication cables 16 to a controller 18. Thecontroller 18 is disposed undersea, close to or on the seabed 20. Inthis respect, it is noted that the elements shown in FIG. 1 are notdrawn to scale and no dimensions should be inferred from FIG. 1.

FIG. 1 also shows that a drill string 24 is provided inside a risersystem 40, that extends from vessel 12 to one or more BOPs 26 and 28. Awellhead 22 of the subsea well is connected to a casing 44, which isconfigured to accommodate the drill string 24 that enters the subseawell. At the end of the drill string 24 there is a drill bit (notshown). Various mechanisms, also not shown, are employed to rotate thedrill string 24, and implicitly the drill bit, to extend the subseawell. The dirt and debris produced by the drill string 24 are removed bycirculating a special fluid, called “mud”, through an inside of thedrill string 24 and then through an annulus formed between the outsideof the drill string 24 and an inside of the riser system 40. Thus, themud is pumped from the vessel 12 through the drill string 24 down to thedrill bit and back through the annulus of the riser system 40 back tothe vessel 12.

The riser system 40 is currently installed in the following way. Thevessel 12 stores plural risers that may be connected one to the other toform the riser system 40. Each riser is lowered through a deck of thevessel 12, substantially perpendicular to the surface of the water. Oncea first riser is immersed into the water, a second riser is attached tothe first riser and further immersed into the water. The process goes onuntil the first riser reaches the equipment at the well head. At thatstage, the first riser is secured to the equipment. Thus, each riser hasto have an external diameter less than an internal diameter of a hole inthe deck or otherwise the riser cannot be lowered through the deck ofvessel 12.

Conventionally, plural pipes are attached to an outside of the riser,e.g., choke line, kill line, blue conduit, yellow conduit, etc. and forma riser assembly. Also, in order to prevent a possible gas bubble topropagate from the well to the vessel, a gas handler may be attached toat least a riser assembly of the riser system 40. Such a riser assembly50 having a riser 51 with a gas handler 52 is shown in FIG. 2. The riser51 has a top end 54 a and a lower end 54 b configured to connect toother risers. FIG. 2 also shows the various lines (pipes) 56 a to 56 dthat run along an outside of the riser 50. Because of the sizelimitations of the deck of the vessel, FIG. 2 shows that the lines 56 ato 56 d are bent and provided at a single side 58 of the gas handler 52in order to reduce an overall exterior diameter of the riser assembly 50to fit through the deck.

However, from a manufacturing point of view, bending the pipes 56 a to56 d as shown in FIG. 2 is time consuming and adds to the overall costof the riser assembly. Accordingly, it would be desirable to providesystems and methods that avoid the afore-described problems anddrawbacks.

SUMMARY OF THE INVENTION

According to one exemplary embodiment, there is a riser assembly to beused in underwater oil and gas exploration. The riser assembly includesa riser having a first end and a second end and a conduit extending fromthe first end to the second end; a gas handler connected to the riserand provided between the first end and the second end, the gas handlerhaving an external casing; plural pipes attached to an outside of theriser such that at least one pipe of the plural pipes enters through theexternal casing; and a gas vent pipe configured to start at the gashandler and extend towards the second end of the riser and the gas ventpipe is further configured to divert a gas from the gas handier throughthe outside of the riser.

According to another exemplary embodiment, there is a gas handlerconfigured to remove gas from a riser. The gas handler includes anexternal casing having first and second ends; a wall provided inside theexternal casing and configured to define an elongated cavity; a pistonconfigured to move along the elongated cavity; a sleeve configured tomove along the elongated cavity, wherein the piston and the sleeve areprovided in a chamber around the elongated cavity; an elastomeric bodyconfigured to be pressed by the piston to close the elongated cavity; agas vent conduit formed in a wall of the external casing and configuredto output the gas; and a conduit formed in a wall of the external casingand configured to extend from the first end to the second end.

According to still another exemplary embodiment, there is a method forassembling a riser assembly. The method includes attaching a gas handlerto a riser having a first end and a second end and a conduit extendingfrom the first end to the second end; attaching plural pipes to anoutside of the riser; connecting at least one pipe of the plural pipesto a conduit formed in an external casing of the gas handler; andconnecting a gas vent pipe to the gas handler such that the gas ventpipe extends towards the second end of the riser and the gas vent pipeis configured to divert a gas from the gas handler through the outsideof the riser.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate one or more embodiments and,together with the description, explain these embodiments. In thedrawings:

FIG. 1 is a schematic diagram of a conventional offshore rig;

FIG. 2 is a schematic diagram of a conventional riser assembly with agas handler;

FIG. 3 is a schematic diagram of a riser assembly having a novel gashandler according to an exemplary embodiment;

FIG. 4 is a schematic diagram of a cap of a gas handler according to anexemplary embodiment;

FIG. 5 is a schematic diagram of a line entering a cap of a gas handleraccording to an exemplary embodiment;

FIG. 6 is a schematic diagram of a line entering a casing of a gashandler according to an exemplary embodiment;

FIG. 7 is a schematic diagram of an interior of a gas handler accordingto an exemplary embodiment;

FIG. 8 is an schematic diagram of a closed piston of a gas handleraccording to an exemplary embodiment;

FIG. 9 is a schematic diagram of a riser assembly according to anexemplary embodiment;

FIG. 10 is a schematic diagram of a cut-through of a gas handleraccording to an exemplary embodiment; and

FIG. 11 is a flow chart of a method for assembling a riser assemblyaccording to an exemplary embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the exemplary embodiments refers to theaccompanying drawings. The same reference numbers in different drawingsidentify the same or similar elements. The following detaileddescription does not limit the invention. Instead, the scope of theinvention is defined by the appended claims. The following embodimentsare discussed, for simplicity, with regard to the terminology andstructure of risers, riser assemblies, and riser systems. However, theembodiments to be discussed next are not limited to these systems, butmay be applied to other systems that require to have an overall exteriordiameter less than a predetermined size.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with an embodiment is included inat least one embodiment of the subject matter disclosed. Thus, theappearance of the phrases “in one embodiment” or “in an embodiment” invarious places throughout the specification is not necessarily referringto the same embodiment. Further, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

According to an exemplary embodiment, a gas handler that is provided ona riser is configured to receive plural pipes such that the plural pipesdo not have to be bent around and brought to one side of the body. Inone application, all the plural pipes enter through a housing of the gashandler in order to pass the gas handler.

According to an exemplary embodiment illustrated in FIG. 3, a riserassembly 70 includes a riser 72 and a gas handler 74. The gas handler 74has an external casing 76 having a predetermined external diameter. Theexternal diameter of the external casing 76 is smaller than a diameterof a hole in a deck through which the riser assembly has to pass. Pluralpipes 78 a-d are provided outside the riser 72 and attached to riser 72by brackets 80. An imaginary cylinder that includes all the pipes has adiameter smaller than the external diameter of the casing 76. A guidebracket 82 may be placed at a bottom end 84 of the riser 72 and anotherguide bracket 86 may be placed at a top end 88 of the riser 72. Thebottom and top ends of the riser are defined relative to a position ofthe riser when provided in the riser system underwater. Other risers areconfigured to be attached to ends 84 and 88 of the current riser 72. Theriser 72 has a conduit 73 that extends from the bottom end 84 to the topend 88 and this conduit is configured to receive a drill line (notshown).

The guide brackets 82 and 86 are used for aligning the plural pipes 78a-d when assembled and holding them secure during pressurization. Moreor less guide brackets may be used. The plural pipes 78 a-d may includea mud boost line, a choke line, a kill line, a yellow conduit line, ablue conduit line. Other lines are also possible. FIG. 3 also showsplural bumper plates 90 a-c that are attached to the riser 72. Thebumper plates are provided between the plural pipes 78 a-d and havecorresponding edges 92 a-c configured to be more elevated than theplural pipes relative to an outer surface of the riser 72. In this way,when the riser assembly 70 is lowered through the deck of the vessel,the plural pipes do not bump into the edges of the deck. It is notedthat due to the continuous movement of the vessel (waves, etc.), whenthe riser assembly is lowered through the deck, the riser assembly isprone to moving and thus hitting the edges of the deck. Thus, the bumperplates protect the plural pipes from being deformed during suchinteractions with the deck.

According to an exemplary embodiment illustrated in FIG. 4, a moredetailed view of the connection between the plural pipes 78 a-d and thegas handler 74 is presented. The casing 76 has an upper cap 100 that maybe attached with bolts 102 to the casing 76. A pipe 78 a is configuredto enter through the upper cap 100 via a hole (not shown). Each pipe ofthe plural pipes 78 a-d may have a corresponding hole in the cap 100.FIG. 5 shows the hole 104 of the cap 100. FIG. 5 also shows that pipe 78a has a collar 106 or other means (a shoulder) that is configured to beaccommodated by hole 104. The collar 106 may be welded to the pipe 78 a.Each pipe 78 a-d may have a similar collar. The hole 104 may have ashoulder 104 a for preventing the pipe 78 a to further enter into thecasing 76.

For maintaining the pipe 78 a in place, i.e., inside the gas handler 74,a plate 108 is configured to be attached to the cap 100, around the pipe78 a. In this way, the collar 106 is prevented to exit the hole 104 andthe pipe 78 a is secured to the cap 100. An appropriate seal or washer105 may be used between the collar 106 and the plate 108. Plate 108 issecured to upper cap 100 by bolts 109. One or more seals 107 may be usedbetween the pipe 78 a and the hole 104 for preventing a fluid inside thepipe 78 a from escaping. According to an exemplary embodiment, the pipe78 a may enter through the cap 100 to reach the casing 76.

The pipe 78 a ends inside the casing 76 as shown in FIG. 6. In otherwords, a conduit 110 is formed through the casing 76, from one end tothe other, for transmitting the fluid under pressure across the gashandler 74. For achieving this goal, the casing 76 is configured to havea receptacle region 76 a having an inner diameter d that fits (plusnormal tolerances) an outer diameter of the pipe 78 a. Receptacle region76 a has an upward facing receptacle shoulder 76 b. The pipe 78 a may bestabbed into the receptacle 76 a. For ensuring that no pressure frominside the pipe 78 a escapes outside, plural seals 112 may be providedat an interface between the pipe 78 a and the receptacle 76 a. The pipe78 a may enter a predetermined depth h into the casing 76. A similararrangement may be provided at the other end of the casing 76 for acorresponding part. Returning to FIG. 5, the riser 70 may be attached tothe cap 100 either by welding or by forming the riser 70 integrally withand the cap 100.

The gas handler 74 is discussed now with reference to FIG. 7. The gashandier 74 has the exterior casing 76 formed to incorporate most if notall of its components. In one application, the exterior casing 76 is acylinder. FIG. 7 shows a lower cap 101 that is attached, similar to theupper cap 100, to the casing 76. FIG. 7 also shows the conduit 110formed through a wall 111 of the casing 76, from the upper cap 100 tothe lower cap 101. A pipe 112 a enters through the lower cap 101 andpartially into the casing 76 to fluidly communicate with the conduit110. The pipe 112 a corresponds to the pipe 78 a and together they form,for example, the kill line or any other line.

The gas handler 74 is configured to remove gas under pressure that mightappear inside the riser 70. If the gas under pressure is not removedfrom the riser, that gas might make its way to the vessel withcatastrophic consequences, e.g., explosion. For this reason, the gashandler 74 is an important safety device of the subsea explorationsystem. The gas that is captured by the gas handler 74 has to be removedfrom the riser 70 and delivered, in a safety way, to a desired location.For example, the gas might be delivered at the surface of the water,away from the vessel. For this reason, a gas vent conduit 116 is formedin the wall of the casing 76 as shown in FIG. 7. The gas vent conduit116 is configured to communicate with a sleeve 118 that has a passage120. As shown in FIG. 7, the sleeve 118 fully closes the gas ventconduit 116 by misaligning the passage 120 with a corresponding port 122of the gas vent conduit 116. In this position, no gas can escape fromthe riser via the gas vent conduit 116.

However, the sleeve 118 may be moved upwards (along axis X), along adirection of the riser, as shown in FIG. 8. In the embodiment shown inFIG. 8, the port 122 of the gas vent conduit 116 is in fluidcommunication with the passage 120 of the sleeve 118. Further, a gasfrom inside the riser may travel through an opening 124 of a piston 126to be discussed later. The piston 126 and the sleeve 118 are provided ina chamber 127 of the gas handler 74. The piston 126 and the sleeve 118are configured to move along axis X as desired by an operator of thewell. The gas from the riser 72 may travel to the gas vent conduit 116as a cavity 128 is provided at an interface between the sleeve 118 andthe piston 126. FIG. 8 also shows a hole 130 (in reality may be pluralholes 130) in a wall 131 that defines a cavity 132. The cavity 132fluidly connects two parts (above and below the gas handler) of theriser 72 and the hole 130 fluidly communicates the cavity 132 (e.g.,inside of the riser 72) with the chamber 127. The cavity 132 may beelongated along the axis X, e.g., have a cylindrical shape.

Under certain circumstances, it is possible that the piston 126 movesupwards as also shown in FIG. 8 for pressing an elastomer body 136 forclosing the communication between the two parts of the riser 70. Whenthis is happening, the gas propagating through the riser is stopped atthe gas handler 74 and this gas is provided to the gas vent conduit 116via the hole 130, opening 124, cavity 128, passage 120, and port 122.This gas further propagates from the gas vent conduit 116 to a gas ventline 140 towards the vessel above. The gas vent line 140 may beconnected to the gas vent conduit 116 in a similar manner as the line 78a is connected to conduit 110.

The gas vent line 140 is shown in FIG. 9 together with the other lines.It is noted that the gas vent line extends from the gas handler 74 onlytowards the upper end 88 of the riser 72 and not towards the lower end84 of the riser 72. Thus, the gas vent line 140 is different from theother lines 78 a-d as this line originates at the gas handler 74.Further, it is noted that any of the lines 78 a-d may be formed from twoportions that are not in direct contact to each other. For example, line78 a may have a first portion 78 a-1 and a second portion 78 a-2. Thesetwo portions are in fluid communication with each other but not indirect contact with each other as shown in FIG. 10. FIG. 10 shows across-section through the gas handler 74 with the external casing 76having a given thickness “t”. In the external casing, the conduit 110 isformed and the conduit 110 connects the first portion 78 a-1 of the line78 a to the second portion 78 a-2 of the same line 78 a. The same may betrue for the other lines 78 b-d. However, in another application, theconduit 110 may be formed not in the wall of the casing 76 but insidethe casing 76.

According to an exemplary embodiment illustrated in FIG. 11, there is amethod for assembling a riser assembly. The method includes a step 1100of attaching a gas handler (74) to a riser (72) having a first end (84)and a second end (88) and a conduit (73) extending from the first end(84) to the second end (88); a step 1102 of attaching plural pipes (78a-d) to an outside of the riser (72); a step 1104 of connecting at leastone pipe (78 a) of the plural pipes (78 a-d) to a conduit (110) formedin an external casing (76) of the gas handler (74); and a step 1106 ofconnecting a gas vent pipe (140) to the gas handler (74) such that thegas vent pipe (140) extends towards the second end (88) of the riser(72) and the gas vent pipe (140) is configured to divert a gas from thegas handler (74) through the outside of the riser (72).

The disclosed exemplary embodiments provide a system and a method forstreamlining an oil and gas exploration process in which a riser systemis used to connect an undersea well to a vessel. It should be understoodthat this description is not intended to limit the invention. On thecontrary, the exemplary embodiments are intended to cover alternatives,modifications and equivalents, which are included in the spirit andscope of the invention as defined by the appended claims. Further, inthe detailed description of the exemplary embodiments, numerous specificdetails are set forth in order to provide a comprehensive understandingof the claimed invention. However, one skilled in the art wouldunderstand that various embodiments may be practiced without suchspecific details.

Although the features and elements of the present exemplary embodimentsare described in the embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the embodiments or in various combinations with or withoutother features and elements disclosed herein.

This written description uses examples of the subject matter disclosedto enable any person skilled in the art to practice the same, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the subject matter is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims.

What is claimed is:
 1. A gas handler for use with a riser assembly,comprising: an external casing having a central passage; an elastomericbody surrounding the passage that is movable by a piston to a closedposition blocking upward flow through the central passage; a gas ventconduit in fluid communication with the central passage; a valve sleevethat selectively blocks and opens fluid communication between thecentral passage and the gas vent conduit; a gas vent pipe configured tostart at the gas vent conduit of the gas handler, and to divert a gasaway from the gas handler; and a plurality of pipes having flow pathsthat pass through the external casing of the gas handler alongside thecentral passage.
 2. The gas handler of claim 1, wherein the gas ventpipe extends upwardly towards the upper end of the riser assembly. 3.The gas handler of claim 1, wherein an external diameter of the casingis larger than a diameter of an imaginary cylinder that encompasses theplurality of pipes.
 4. The gas handler of claim 1, wherein the pluralityof pipes include a choke line, a kill line, and hydraulic fluidconduits.
 5. A gas handler for use with a riser assembly, comprising: anexternal casing; a plurality of pipes configured so that at least onepipe of the plurality of pipes enters through the external casing, theat least one pipe made of a first portion and a second portion that arenot in direct contact with each other; a gas vent pipe configured tostart at the gas handler, and to divert a gas away from the gas handler;and a lower cap and an upper cap configured to be attached to theexternal casing.
 6. The gas handler of claim 5, wherein the firstportion enters through the lower cap and the second portion entersthrough the upper cap and a conduit formed in a wall of the externalcasing fluidly communicates the first portion with the second portion.7. The gas handler of claim 5, further comprising a receptacle regionprovided in the upper cap for receiving the at least one pipe, thereceptacle region being configured to partially enter into a wall of theexternal casing of the gas handler and to fluidly communicate with aconduit formed in a wall of the external casing of the gas handler. 8.The gas handler of claim 7, wherein a portion of the at least one pipehas a collar configured to enter into the receptacle region.
 9. The gashandler assembly of claim 7, further comprising at least one sealbetween the receptacle region and the external casing for preventing afluid inside the at least one pipe to escape outside.
 10. A gas handlerconfigured to remove gas from a riser, the gas handler comprising: anexternal casing having first and second ends; a wall provided inside theexternal casing and configured to define an elongated cavity; a pistonconfigured to move along the elongated cavity; a sleeve configured tomove along the elongated cavity, wherein the piston and the sleeve forma chamber for hydraulic control fluid around the elongated cavity; anelastomeric body configured to be pressed by the piston to close theelongated cavity; a gas vent conduit formed in a wall of the externalcasing and configured to output the gas; and a conduit formed in a wallof the external casing and configured to extend from the first end tothe second end.
 11. The gas handler of claim 10, further comprising: afirst cap configured to be attached to the external casing at the firstend; and a second cap configured to be attached to the external casingto the second end.
 12. The gas handler of claim 11, further comprising:a receptacle region provided in the first cap or the second cap andpartially into the wall of the external casing, wherein the receptacleregion is configured to receive a pipe, external to the gas handler, andto fluidly connect the pipe to the conduit.
 13. The gas handler of claim11, wherein at least one pipe is made of a first portion and a secondportion that are not in direct contact with each other and the firstportion enters through the first cap and the second portion entersthrough the second cap and the conduit formed in the wall of theexternal casing fluidly communicates the first portion with the secondportion.
 14. The gas handler of claim 10, further comprising: areceptacle region provided in the external casing for receiving at leastone pipe, the receptacle region being configured to partially enter intothe wall of the external casing of the gas handler and to fluidlycommunicate with the conduit formed in the wall of the external casingof the gas handler.
 15. The gas handler of claim 14, wherein a portionof the at least one pipe has a collar configured to enter into thereceptacle region.
 16. The gas handler of claim 14, further comprising:at least one seal between the receptacle region and the external casingfor preventing a fluid inside the at least one pipe to escape outside.